About this replacement
Cobra FRS120 / FRS117 / FRS225 — 4.8V Ni-MH Replacement Battery (FA-AA)
This is a 4.8V, 800mAh Ni-MH battery pack for the Cobra FRS120, FRS117, and FRS225 consumer two-way radios. It replaces OEM part numbers FA-AA and COM-FAAA. The pack slots directly into the radio's battery compartment and restores full transmit and receive function.
- FRS120, FRS117, and FRS225 compatibility: These three Cobra models share the same battery bay dimensions and 4.8V four-cell Ni-MH voltage rail. The connector pinout and physical form factor are identical across all three, so one pack covers the full group.
- Bench tested on actual hardware: We cycled this pack through transmit loads on an FRS120 body. The cells held voltage through repeated PTT bursts without triggering the radio's low-battery cutoff, and the charger accepted the pack on first insertion without error.
- First cycle on Ni-MH packs: Ni-MH cells ship at partial charge. Run the radio until the low-battery indicator shows, then charge to full before the second use — this lets the cells balance and reach rated capacity faster than partial top-ups from new.
Why the FRS120 cuts out mid-transmission on a fresh pack
When you press PTT, transmit current spikes sharply — well above the current draw during standby or receive. A Ni-MH pack that shipped at low storage voltage can't sustain that spike cleanly. The radio's internal protection circuit sees the voltage dip as a fault condition and drops the transmission. This is not a defective battery — it's a storage-state issue. Charge the pack fully before the first PTT use and the cutout stops.
Bar indicator showing one fewer bar than expected after install
The FRS120 reads voltage thresholds and maps them to bar segments on the display. A new Ni-MH pack sitting at storage voltage — typically around 4.6V — falls below the threshold the radio expects for a full reading, so it displays one bar short. This is not a capacity fault. Put the pack through a full charge cycle first; resting voltage rises to the expected range and the bar indicator catches up.